Table 2.

Sample Characteristics

Characteristic	Percentage
Demographic
Mean age (SD), y	76 (7)
Race
White	91
Black	6
Other	3
Region
West, Pacific West	11
West, Mountain West	5
Midwest, West North Central	7
Midwest, East North Central	19
Northeast, New England	7
Northeast, Mid-Atlantic	16
South, South Atlantic	21
South, West South Central	9
South, East South Central	5
Not known	1
Clinical
No comorbid diseases	32
Axillary lymph node involvement	39
Sentinel lymph node biopsy	55
Radiotherapy	73
Chemotherapy	13
Socioeconomic
Mean income (SD), $US	43,429 (10,649)
Education
Mean percent completed less than ninth grade (SD)	7 (4)
Mean percent completed college or higher (SD)	24 (9)
Mean surgeon density (per 100,000) (SD)	13 (10)
Mean radiation oncologist density (per 100,000) (SD)	1.5 (1.4)

SD indicates standard deviation.